Secondary Organising Pneumonia Among COVID-19 Patients: A Retrospective Case-Control Study

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Secondary organising pneumonia (OP) induced by SARS-CoV-2 infection is a recently recognised complication of COVID-19. We aimed to evaluate the prevalence of OP among hospitalised patients with COVID-19 pneumonia and to assess whether disease severity and other clinical factors and comorbidities are correlated with OP development. We conducted a retrospective case-control study including hospitalised patients due to COVID-19 who performed a chest CT scan during hospitalisation and compared patients with clinical and radiological evidence of OP to patients without evidence of OP. Demographics, comorbidities, disease severity, dexamethasone/remdesivir treatment, laboratory results, and outcomes were compared between groups. One hundred fifteen patients were included, of whom 48 (41.7%) fulfilled clinical and imaging criteria for OP. Among OP patients, the most common chest CT-scan findings were consolidations, arciform condensations, and subpleural bands. OP patients had longer hospitalisation (19.5 vs 10 days, p=0.002) and more frequent ICU admission, but no significant differences in readmittance or mortality rates within 180 days compared to controls. In the adjusted effects model, the need for supplementary oxygen on the 21^st day after symptom onset, the presence of Ordinal Scale for Clinical Improvement (OSCI) = 4, when compared to OSCI ≤ 3, and higher C-reactive protein on admission, were significantly associated with higher odds for OP. No other differences were identified between OP and controls after adjusting for other factors. The use of remdesivir or dexamethasone did not impact the diagnosis of OP. Only 38% of OP patients required treatment with high-dose corticosteroids. In conclusion, SARS-CoV-2-induced OP may be more frequent than previously thought, especially among hospitalised patients and patients with a more severe disease, particularly those who fail to improve after the second week of disease or who present higher inflammatory markers on admission. It increases the length of stay, but not all patients require specific treatment and OP may improve despite the absence of high-dose corticosteroid treatment.